The present invention relates to improvements in the art of wrapping objects in plastic film, and more particularly in forming a package having reclosable rib and groove interlocked plastic fasteners extending therealong.
A substantial number of developments have been made for the continuous packaging of products such as food products wherein a continuous length of film is wrapped around the package and cross-sealed to complete the closure.
One form of this type of development is known as a form, fill and seal machine, and while a substantial number of these machines operate vertically with the product dropped into the tube formed from the film, other form, fill and seal machines have been employed which operate horizontally.
To gain access to the product in the packages where the product has been wrapped by a plastic film, the film must be cut or otherwise broken open. If it is desired to replace into the opened wrapper the remainder of the product which has not been consumed, assuming the wrapper has not been destroyed in opening it, the remainder of the product must be at least partially exposed to atmosphere and subject to drying out or other deterioration due to the exposure. Because the wrapper generally snugly engages the article, it is difficult to withdraw the article from the partially ruptured wrapper so that the tendency is for the consumer to virtually destroy the wrapper to gain access to the article even though only partial use of the article is contemplated. This may require rewrapping in foil or household wrapping film in an attempt to retain freshness.
Although zipper equipped bags have been known for some time and widely used both for commercially packaged products and unfilled bags, there is need for a package which can be continuously made wherein the package is provided with a reopenable feature such as a continuous zipper along the side. Inasmuch as the zipper is openable by pulling apart on opening pull flanges, it is further desirable that a means be made so that the package is tamper-evident by requiring that the film be severed between the zipper profiles before using. This insures a hermetic seal until the product is first used and provides a means whereby the purchaser can immediately perceive whether or not the product has been tampered with or opened prior to purchase.
A further need for such product packages is that they be smooth and streamlined so that they can be stacked and handled in an easy manner. While once the package is first opened it is convenient to have the pull flanges of the zipper be upstanding, prior to the first use, it is desirable that the zipper be flat against the package so that the package has a better appearance and is easier to handle.
By way of example, U.S. Pat. No. 3,274,746 is referred to as representative of existing conventional horizontal form, fill and seal apparatus for packaging relatively heavy articles such as cheese in plastic film or the like. The method there disclosed consists in running the wrapper sheet in the form of a continuous strip along a horizontal packaging line wherein the wrapper sheet is wrapped about the product articles successively placed thereon in spaced units, by folding the sheet from opposite sides onto the articles and sealing the opposite longitudinal margins of the sheet together. Finally, the sheet which has, in effect, been sealed into a tubular envelope about the articles, is sealed across the envelope between the articles and separated into sealed individual article containing package units. This mode of packaging has been practiced for a long time without any significant change in the package in spite of the disadvantages previously mentioned.
Attention is also directed to U.S. Pat. Nos. 4,240,241 and 4,246,288 which disclose a technique for packaging according to which semi-rigid receptacles are formed in one layer of plastic web and a cover sheet is sealed marginally to each receptacle, the receptacle and the cover sheet having an interlocking rib and groove closure strip, i.e. zipper, so that when the sealed package is opened the same may be reclosed by means of the zipper. However, that technique involves a very different form, fill and seal apparatus than the virtually standard horizontal form, fill and seal machines which have long been used for sealing various food products, and in particular cheese. Therefore, in order to adopt the packaging of these two patents, the horizontal form, fill and seal machines now extensively used would have to be scrapped and the investment therein lost. The very large capital investment for installing machines adapted for producing reclosable packages according to these patents presents a formidable deterrent to their adoption.
Bags equipped with resiliently flexible zipper means have been provided for receiving various food and nonfood products and adapted for access into the tops of the bags by opening the zipper. U.S. Pat. Nos. 3,198,223 and 3,462,332 show representative structures in which the zipper profiles are extruded integrally with the bag wall material or fused with the film or bag wall material at extrusion. U.S. Pat Nos. 2,780,261, 3,054,434, 3,198,228, 3,347,298 and 3,886,633 disclose means for easy opening of the zippers externally of the bag but resistant to opening from separating forces generated as by means of the contents internally of the bag.
U.S. Pat. Nos. 3,780,781 and 3,948,705 represent structures wherein the zipper profile strips have base flanges which are fused to the bag wall film material.
U.S. Pat. No. 4,372,793 exemplifies adhesive attachment of the zipper strips to the bag film or side wall material.
U.S. Pat. Nos. 2,780,261, 2,871,539, 3,325,084, and 3,886,633 show examples of multiprofile zippers.
U.S. Pat. Nos. 3,226,787, 3,685,562, 3,827,472 and 3,625,270 disclose a tear strip structure to facilitate opening bags.
U.S. Pat. No. 4,589,145 shows another example of the formation of a flat package with a zipper opening, although the zipper projects from the side of the package.
None of the foregoing patents meet the objectives and advantages of the present invention.
An object of the present invention is to provide an improved method and apparatus for the simplified formation of continuous packages for wrapping items such as blocks of cheese or similar foodstuffs in a continuous manner wherein the package is furnished with a reopenable zipper which is carried flattened against the finished package in a manner to provide a streamlined package facilitating easy storage and handling.
A still further object of the invention is to provide an improved method and apparatus for the continual enclosure of items in film with the finished package having a reopenable zipper therealong which has tamper-evident capabilities showing the purchaser whether the package has been previously opened or not.